/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.06.05 01:44:48
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

int main() {
    int n,p;cin >> n >> p;
    vector<vector<double>> dp(n+1,vector<double>(p+1,0));
    dp[0][0] = 0;
    for (int i = 0; i < n; i++) {
        int a,b,c;cin >> a >> b >> c;
        for (int j = 0; j <= p; j++) {
            dp[i + 1][j] = (dp[i][j] * i + a) / (i + 1);
            if (j - 1 >= 0) dp[i + 1][j] = min(dp[i + 1][j],(dp[i][j-1] * i + b) / (i + 1));
            if (j - 2 >= 0) dp[i + 1][j] = min(dp[i + 1][j],(dp[i][j-2] * i + c) / (i + 1));
            if (j - 3 >= 0) dp[i + 1][j] = min(dp[i + 1][j],(dp[i][j-3] * i + 1) / (i + 1));
        }
    }
    printf("%.10f",dp[n][p]);
    return 0;
}